1. Field of the Invention
The present invention relates to a method and an apparatus for correcting an alignment error of a scanning head of a shuttle type scanner and, more particularly to a method and an apparatus for correcting an alignment error of a scanning head of a shuttle type scanner capable of compensating an error occurred in a manufacturing process of a product or the alignment error generated by an impact applied in use.
2. Description of the Related Art
Conventionally, a scanning head having an optical sensor in a shuttle type scanner is transported exactly transverse to a document transporting (feeding) direction. This means that there should be an alignment error equal to zero (0), or no alignment error. Thus, the image distortion does not occur in the scanned image data. Since it is impossible, however, to manufacture a perfect product which has no alignment error due to a manufacturing process or other reasons, the shuttle scanners which are currently being produced are designed to ignore an alignment error within a predetermined limit. Here, the limit of the alignment error varies according to manufacturers of a relevant product and each product. The alignment error limit is roughly set .PHI.&lt;4.degree. wherein, .PHI. is an error angle. Accordingly, a product having an alignment error exceeding this limit, it is regarded as an inferior product and a process for mechanically rearranging the alignment error is performed. In the case of a product having the alignment error within this limit, even if the alignment error occurs, it is ignored and the product can be used.
However, in the conventional shuttle type scanner, there is no method for correcting the alignment error regarding the products having the alignment error within the permitted limit. As a result, since the product is continuously used ignoring the alignment error, when a document in a normal state is scanned and the scanned image data is printed, image distortion can occur in the printed image.
It is well known in the art to use the scanner's optical sensor to check for and correct for misalignment of a printing head in a multifunction machine having an optical sensor and ink cartridge, as evidenced by U.S. Pat. No. 5,250,956 to Robert D. Haselby et al. entitled Print Cartridge Bidirectional Alignment In Carriage Axis, U.S. Pat. No. 5,297,017 to Robert D. Haselby et al. entitled Print Cartridge Alignment In Paper Axis and U.S. Pat. No. 5,644,344 to Robert D. Haselby entitled Optical-Print Cartridge System. I have determined, however, that should the print cartridge of the prior art be properly aligned and the optical sensor misaligned, then print cartridge alignment will be changed unnecessarily, resulting in a distorted printed image.